You can tell that by the 4th, 5th and 6th characters of the serial number, which will always be numbers.

4 = the last digit of the year...2014. Now of course it could also be 1994 or 2004, or someday 2024, so you will need to have a ballpark idea of how new the notebook is and what hardware was around at the time.

The 5th and 6th digits are the week of production during the year. They will always range from 01 - 52.

Use this guide for how to find the product number/model number of your notebook.